1. Field of the Invention
This present invention relates in general to the field of programmable robotic manipulators, and assist devices that can interact with human operators.
2. Description of Related Art
Intelligent Assist Devices (“IADs”) are computer-controlled machines that aid a human worker in moving a payload. IADs may provide a human operator a variety of types of assistance, including supporting payload weight, helping to overcome friction or other resistive forces, helping to guide and direct the payload motion, or moving the payload without human guidance.
IAD characteristics have been fully described in the following commonly owned U.S. Patent Applications: U.S. patent application Ser. No. 09/781,801, titled “MODULES FOR USE IN AN INTEGRATED INTELLIGENT ASSIST SYSTEM”, filed Feb. 12, 2001, now U.S. Pat. No. 6,813,542, issued Nov. 2, 2004; U.S. patent application Ser. No. 09/781,683, titled “SYSTEM AND ARCHITECTURE FOR PROVIDING A MODULAR INTELLIGENT ASSIST SYSTEM,” filed Feb. 12, 2001, now U.S. Pat. No. 6,928,336, issued Aug. 9, 2005; U.S. patent application Ser. No. 10/147,141, titled “INTENT SENSOR FOR INTELLIGENT ASSIST DEVICES,” filed May 16, 2002, now U.S. Pat. No. 6,738,691, issued May 18, 2004; and U.S. Pat. No. 10/431,582, titled “METHODS AND APPARATUS FOR MANIPULATION OF HEAVY PAYLOADS WITH INTELLIGENT ASSIST DEVICES,” filed May 8, 2003, currently pending, the contents of which are all incorporated by reference herein in their entireties.
IADs typically use controllers that are closed loop systems. Any given controller is programmed to allow the IAD to operate efficiently and effectively. However, closed loop systems may make the IADs susceptible to instability, such as self-sustained or growing oscillations within the IAD. Whether or not instability will occur within a particular system depends on various system parameters and dynamic effects. Although instability in IADs is undesirable, current systems do not address instability. As a result, current IADs may not be capable of maintaining peak performance for a wide range of system parameters.